ML20247G411

Transit Time Flow Meter Calculations

ML20247G411
Person / Time
Site:	Comanche Peak
Issue date:	03/31/1989
From:	Tuley C WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
To:
Shared Package
ML19297H472	List: ML20247G395 ML20247G401 ML20247G411
References
WCAP-12229, NUDOCS 8904040219
Download: ML20247G411 (5)

Text

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WESTINGHOUSE CLASS 3 i

WCAP-12229 i

s TRANSITTIMEFLOWMETER(TTFM)

CALCULATIONS

\

l March, 1989 C. R. Tuley 8904040219 8?/5331 ~'

h) PDR ADOCK 05000445 A PDC n.... ,,_

WESTINGHOUSE ELECTRIC CORPORATION Power Systems i P. O. Box 355 l

Pittsburgh, Pennsylvania 15230 f

l l

} Per an NRC requirement specified at a Texas Utilities / Westinghouse /NRC l

meeting on 10/11/84, Westinghouse has included an "NRC conservatism factor" 4 in the determination of the minimum RCS Flow that Comanche Peak must verify at the beginning of a cycle. There was some concern expressed by the NRC staff concerning the magnitude of the uncertainty of the Azimuthal Velocity Profile for the Transit Time Flow Meter (TTFM). Westinghouse includes an allowance of [

)+a,c. The NRC specified that a value of [ -]+a,c be used as the accuracy of the TTFM on a single loop basis. Westinghouse calculates that the accuracy of the TTFM is [ ]+a,c on a single loop basis. Using the NRC specified value, and assuming that the conservatism factor is treated as a random, j loop independent parameter allows the determination of the magnitude of the "NRC conservatism factor". This value is:

x.[ .]+a,c

.[ )+a,c, The value for X is then included with the random uncertainties associated with the use of the TTFM. These are:

Fluid Flow - -

+a,c Radial Velocity Profile -

Cross Flow -

Mechanical Detector Spacing and Detector /Collimator Angle - 1 Pipe Internal Cross Sectional Area -

Data Collection Statistics -

Data Reduction -

Using the Square Root of the Sum of the Squares (SRSS) technique, these

, uncertainties total [ ]+a,c. The systematic uncertainty for l the Azimuthal Velocity Profile is as noted above.

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l l

The random and systematic components of the TTFM uncertainty are utilized 4 twice in the calculation of the precision RCS Flow measurement uncertainty. The first utilization is in the determination of [

]+a,c. The second time they are used is in the

[ ]+a,c. In both instances, ,

the NRC specified conservatism factor is an integral part of the TTFM random uncertainty. In fact, an investigation of the uncertainties listed on the previous page will result in the conclusion that the NRC specified l conservatism factor is the largest component of the SRSS of the TTFM random uncertainties. Inclusion of the conservatism factor increases the SRSS of the TTFM random uncertainties by [ ]+a,c, The precision RCS Flow measurement uncertainty is then combined with the uncertainty associated with the use of the Cold Leg Elbow Taps. The j uncertainty for use of one Elbow Tap per loop, indicated via the plant process computer is comb ued (via SRSS) with the precision RCS Flow measurement uncertainty. This combination forms the total RCS Flow measurement uncertainty.

The difference between the total RCS Flow measurement uncertainty, with and without the conservatism factor, is significant. With the conservatism factor, the total uncertainty is [ ]+a,c. Without the conservatism factor, the total uncertainty is [ ]+a,c. The value with the conservatism factor is used to determine the minimum measured flow at the beginning of the cycle, i.e., the plant must measure X gpm where X includes an allowance of [. ]+a,c for measurement uncertainty.

Based on the above discussion, Westinghouse believes that the NRC specified conservatism factor has been appropriately determined and included in the

, calculation of the uncertainty for the TTFM and subsequently the precision

,' RCS Flow measurement uncertainty and the total RCS Flow measurement

uncertainty. In addition, this conservatively determined uncertainty has

.- . been appropriately specified in the Comanche Peak Technical Specifications to assure that the minimum flow present in the plant exceeds the analysis

.'4 assumptions.

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